1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copying machine or a printer, an image forming method, and a computer program product for forming a color image.
2. Description of the Related Art
Conventionally, when a color registration adjustment process is to be performed to detect a superimposed state of images of different color components, it is determined whether a predetermined time has elapsed since a previous adjustment process, whether a predetermined number of images have been formed, whether environment has changed, and whether power on/off operation has been performed. Thereafter, when it is expected that the quality of an image to be formed may fail out of an appropriate range, a test image is formed and the quality of the test image is checked. When the quality of the test image is out of the appropriate range, the color registration adjustment process is performed.
For example, there is a disclosed technology for color registration adjustment, in which a color registration process is performed only when the quality of an image to be formed is likely to fall out of an appropriate range, in order to reduce wasteful consumption of a developer and the like and to efficiently adjust the color registration (see, for example, Japanese Patent Application Laid-open No. 2004-117384).
In the conventional color registration adjustment process as described above, the color registration process is performed when it is expected that the quality of an image to be formed may fall out of an appropriate range depending on the environment (temperature). However, if an image forming apparatus includes a plurality of writing units, temperature information of each writing unit is not taken into account when the color registration is adjusted. Therefore, the color registration adjustment process cannot appropriately be performed with consideration of a temperature difference between the writing units.
The present invention has been made in view of the above, and there is a need to provide a technology that enables an image forming apparatus having a plurality of writing units to accurately adjust color registration with consideration of a temperature difference between the writing units.